Treesearch

Locations within forest fires that remain unburned or burn at low severity—known as fire refugia - are important components of contemporary burn mosaics, but their composition and structure at regional scales are poorly understood. Focusing on recent, large wildfires across the US Pacific Northwest (Oregon and Washington), our research objectives are to (1) classify fire refugia and burn severity based on relativized spectral change in Landsat time series; (2) quantify the pre-fire composition and structure of mapped fire refugia; (3) in forested areas, assess the relative abundance of...

Southern California chaparral environments, with steep mountain slopes, semi-arid climate, and non-cohesive soils, are very erosive landscapes. Wildfire is the dominant ecological disturbance event in chaparral and it greatly accelerates flooding and erosion, which are directly and/or indirectly related to the loss of the protective vegetation. Since the 1920s, dams and debris basins have been constructed by public works agencies to protect the growing population and infrastructure of southern California by intercepting and impounding flows of water and debris. Dams also capture stream...

Dormant seeds in the soil are an important contribution to the regenerative potential of an area. Understanding factors that affect seed bank dynamics in arid regions provides insight into how communities respond to disturbance and environmental change. We characterized seed banks in a Great Basin sagebrush steppe system, using field surveys and seed bank studies to compare 17 sites that differed in above-ground vegetation, fire history, and grazing use. We asked whether shrub cover, ground cover, climate, or disturbance history were predictive of seed densities, diversity, the presence of...

1. Climate change vulnerability assessments are commonly used to identify species or populations at risk from global climate change, but few translate impact assessments to climate change adaptation actions. Furthermore, most climate change adaptation efforts emphasize where to implement management actions, whereas timing remains largely overlooked. The rate of modern climate change introduces urgency in evaluating whether delaying conservation actions compromises theirefficacy for reaching important conservation targets.2. We evaluated the importance of multiple climate change adaptation...

Pyrenophora semeniperda can infect nondormant Bromus tectorum seeds under optimal germination conditions, but most escape mortality. This reduces pathogen fitness relative to infection of dormant seeds, which are almost always killed. However, field experiments showed that a large proportion of seeds killed following inoculum addition were not accounted for as dormant seeds, but instead were likely nondormant seeds that would have germinated without inoculum addition. We hypothesized that widely fluctuating water availability to seeds would favor pathogenesis by delaying germination and...

The complex and interdisciplinary nature of socio-environmental (SE) problems has led to numerous efforts to develop organizing frameworks to capture the structural and functional elements of SE systems. We evaluate six leading SE frameworks, i.e., human ecosystem framework, resilience, integrated assessment of ecosystem services, vulnerability framework, coupled human-natural systems, and social-ecological systems framework, with the dual goals of (1) investigating the theoretical core of SE systems research emerging across diverse frameworks and (2) highlighting the gaps and research...

Skipjack Herring (Alosa chrysochloris) has long been proposed as the sole host for Reginaia ebenus (Ebonyshell) and Elliptio crassidens (Elephantear), but these relationships were unconfirmed because of difficulties with maintaining this fish species in captivity. We confirmed the suitability of Skipjack Herring as host for both mussel species, and we also showed that Alabama Shad (Alosa alabamae) is an additional suitable host for E. crassidens; both fish species produced large numbers of juvenile mussels. No other fish species tested (n =12) were suitable hosts for either mussel species....

This is the executive summary of a three-volume science synthesis that addresses various ecological and social concerns regarding management of federal forests encompassed by the Northwest Forest Plan (NWFP). Land managers with the U.S. Forest Service provided questions that helped guide preparation of the synthesis. It builds on the 10-, 15-, and 20-year NWFP monitoring reports and synthesizes the vast body of relevant scientific literature that has accumulated in the 24 years since the NWFP was initiated. Here we summarize scientific findings and considerations for management that were...

During the last two centuries, thousands of insect species have been transported (largely inadvertently) and established outside of their native ranges worldwide, some with catastrophic ecological and economic impacts. Global variation in numbers of invading species depends on geographic variation in propagule pressure and heterogeneity of environmental resistance to invasions. Elton's diversityinvasibility hypothesis, proposed over sixty years ago, has been widely explored for plants but little is known on how biodiversity affects insect invasions. Here we use species inventories from 44...

The amount of biomass stored in forest ecosystems is a result of past natural disturbances, forest management activities, and current structure and composition such as age class distributions. Although natural disturbances are projected to increase in their frequency and severity on a global scale in the future, forest management and timber harvesting decisions continue to be made at local scales, e.g., the ownership or stand level. This study simulated potential changes in natural disturbance regimes and their interaction with timber harvest goals across the Superior National Forest (SNF)...